The invention relates to a method for feeding a gas into a metallurgical vessel, a condensable and/or evaporable component in the gaseous and/or liquid state being entrained by the gas, and the gas being fed to the metallurgical vessel via one or more gas supply means, and to a gas supply means for carrying out the method.
Metallurgical vessels, in particular melter gasifiers, are fed an oxygen-containing gas, for example air or oxygen-enriched air or technical-grade oxygen, via gas nozzles. For process control purposes and to influence the method, it is necessary for a condensable or evaporable component to be blown into the metallurgical vessel together with the corresponding gas. This component is generally formed by water or steam.
A melter gasifier is fed with steam in order to allow the flame temperatures at the oxygen nozzles to be influenced. Since steam is not always available, a further possibility is to supply liquid water in atomized form. In the case of water in the liquid state, as well as the endothermic gasification reaction (H2O+C== greater than H2 +CO) which takes place in any case, the heat of evaporation which is to be applied after the water has been blown in additionally serves to influence the temperature.
However, with both measures there is a risk of water which has condensed or is still liquid flowing through the nozzle passage to the refractory material of the melter gasifier, where it can damage the masonry work. Early atomization does not solve this problem, since the water constantly reaches the inner wall of the nozzle passage, where it forms a film of water.
Therefore, the object of the present invention is to provide a method, of feeding gas which contains a condensable and/or evaporable component in the gaseous and/or liquid state entrained therein in which possible damage to the gas supply means is considerably reduced or prevented altogether.
This object is achieved by the fact that if there are a number of the gas supply means, in each of these gas supply means
in a first section the gas velocity is continuously increased,
in a turbulence zone the gas is intimately mixed with the condensable and/or evaporable component, and
the gas which has been intimately mixed with the entrained component is blown into the metallurgical vessel.
If the component is originally used in the gaseous state, the method according to the invention reliably makes it possible to distribute liquid which has condensed out of the gas phase uniformly in the gas stream, since it is no longer possible for a film of liquid to be deposited in the turbulence zone. The flow conditions and temperatures which then prevail mean that it is also no longer possible for a film of liquid to be deposited again downstream of the turbulence zone.
The method according to the invention also allows the component to be used in the liquid state, for example to be sprayed into the gas stream. Costs can be saved by the absence of a separate evaporation step.
A preferred embodiment of the method according to the invention consists in the gas being formed by oxygen, in particular technical-grade oxygen, as is obtained, for example, from an air fractionation installation.
The condensable and/or evaporable component is preferably formed by steam or water.
According to a further advantageous embodiment, the gas velocity downstream of the first section and upstream of the turbulence zone is kept substantially constant for a period of time.
According to another advantageous embodiment, the gas velocity upstream of the first section is kept substantially constant for a period of time.
According to another embodiment, the gas velocity is kept substantially constant or falls slightly over the exit section.
The invention also relates to a gas supply means for feeding a gas into a metallurgical vessel, the gas supply means having a flow passage passing through it along a central longitudinal axis, and a condensable or evaporable component being entrained by the gas.
In this gas supply means, the intention is to considerably reduce or prevent altogether any possible damage during operation.
To achieve this object, according to the invention a gas supply means of this type is characterized in that the flow passagexe2x80x94starting from a defined cross sectionxe2x80x94has at least
an abrupt cross-sectional widening in the flow passage, and
an exit section which is arranged downstream of the cross-sectional widening, as seen in the direction of flow of the gas, and
a narrowing section, which has a cross section of flow which narrows in the direction of flow of the gas, being arranged upstream of the cross-sectional widening in the direction of flow of the gas.
In this context, an abrupt cross-sectional widening is to be understood as meaning a sudden increase in the diameter of the flow passage which takes place in the direction of flow of the gas. As a result of the swirling and turbulence which occur in the gas, gas constituents which were not fully mixed with the gas by this point are intimately mixed with the gas. In addition, any liquid deposits on the inner wall of the flow passage are entrained thereby and are likewise distributed uniformly in the gas.
Neither for the method according to the invention nor for the gas supply means according to the invention is it necessary for all the sections of a gas supply means mentioned above and below to be structurally combined in a nozzle.
For example, it is possible for the first section or the narrowing section to be arranged upstream of the nozzle and for the exit section to be arranged downstream of the nozzle. The reduced service life of the nozzle and/or the refractory material resulting from this less optimal arrangement may nevertheless be adequate for certain applications. Thus, it should be understood that the gas supply means according to the invention is to be regarded in the most general sense as a gas supply system including one or more gas supply devices having operational characteristics as described herein, and to be inclusive of all physical realizations by which these operating characteristics are realized, in addition to those specifically described.
According to an advantageous configuration, an intermediate section of substantially constant cross section of flow is arranged between the narrowing section and the abrupt cross-sectional widening.
This intermediate section means that the abrupt cross-sectional widening is situated at an optimum distancexe2x80x94with a view to achieving optimum turbulence and to avoiding a film of liquid in the exit sectionxe2x80x94from the gas supply means opening which is on the melter gasifier side.
The abrupt cross-sectional widening is advantageously refined in such a manner that the increase in the cross section of flow at the abrupt cross-sectional widening has a mean inclination xcex1xe2x80x94with respect to the longitudinal axis of the flow passagexe2x80x94of at least 60xc2x0, preferably of at least 75xc2x0.
With an inclination a of at least 60xc2x0, a step is formed on the inner wall of the flow passage, ensuring sufficient atomization of deposited or entrained liquid and then sufficient turbulence and mixing of the gas components.
It is particularly advantageous if the increase in the cross section of flow at the abrupt cross-sectional widening has a mean inclination xcex1 of substantially 90xc2x0.
90xc2x0 does not represent the maximum upper limit for the inclination xcex1; higher values for xcex1 under certain circumstances lead to expedient embodiments. Although higher values for xcex1 result in a sharper break-off edge, if xcex1 greater than 90xc2x0 this edge becomes worn more easily than if xcex1xe2x89xa690xc2x0.
According to one embodiment of the gas supply means according to the invention, an entry section of substantially constant cross section of gas flow is arranged upstream of the narrowing section, as seen in the direction of flow of the gas.
A further aspect of the present invention relates to a device for feeding a gas into a metallurgical vessel, the device comprising one or more gas supply means according to the invention, as well as gas feed lines leading to the gas supply means and means for introducing a condensable or evaporable component into the gas supply means.
To make it possible to benefit from the advantages of the invention, it should not be necessary to completely exchange existing nozzles for gas supply means according to the invention. Rather, it is to be possible, in a simple and inexpensive way, to convert existing nozzles to form gas supply means according to the invention.
Therefore, the invention also relates to an insert piece for converting a nozzle which is known from the prior art, the nozzle passage of which has at least
an exit section, and
a narrowing section, which is arranged upstream of the exit section and whichxe2x80x94towards the cross section of the exit sectionxe2x80x94is designed to taper in the direction of flow of the gas.
An insert piece of this type is characterized in that a gas flow passage is guided through the insert piece along an axis whichxe2x80x94with the insert piece having been inserted into the nozzlexe2x80x94coincides with the central longitudinal axis of the nozzle, at least a partial region of the inner contour of the narrowing section being reproduced by the outer contour of the insert piece, the cross section of the gas flow passage being designed to narrow in the direction of flow of the gas, and the outlet opening being provided with a break-off edge, with the result thatxe2x80x94with the insert piece having been inserted into the nozzlexe2x80x94an abrupt cross-sectional widening arranged downstream of the narrowing section, as seen in the direction of flow of the gas, is formed in the gas flow passage.
Accordingly, in this context the term break-off edge is to be understood as meaning, mutatis mutandis, the designs given above in relation to the abrupt cross-sectional widening.
The insert piece described above can easily be pushed into an existing nozzle, for example during a maintenance shut down with the gas feed line removed. Since the outer contour of the insert piece is accurately shaped to match the inner contour of the nozzle passage, and specifically in particular of the narrowing section or at least a part thereof, when the nozzle begins operation the insert piece is pressed against the narrowing section by the gas pressure.
The gas flow passage, or its part which narrows in the direction of flow of the gas, then forms the narrowing section of the converted nozzle, while the break-off edge of the insert piece forms the abrupt cross-sectional widening of the nozzle.
Advantageously, the outer contour of the insert piece additionally reproduces a partial region of the inner contour of the exit section, the inner contour of which then forms the intermediate section of the converted nozzle.
As an alternative or in addition, according to an advantageous embodiment the outer contour of the insert piece reproduces a partial region of the entry section.
Depending on which additional partial regions of sections are reproduced by the outer contour of the insert piece, either the location of the break-off edge or the abrupt cross-sectional widening is thereby determined in the converted nozzle, and/or a part created is overall more solid, easier to handle and can be inserted accurately into the nozzle.
Compared to nozzles which are known from the prior art, nozzles of the device according to the invention have a smaller cross section immediately upstream of the abrupt cross-sectional increase. Consequently, the admission pressure in the feed line which supplies the nozzle is higher than in the prior art, and thereforexe2x80x94if the supply pressure is constantxe2x80x94the pressure difference at the flow-regulating member, which is situated upstream of the nozzles, is lower. This flow-regulating member, which for all the nozzles restricts the supply pressure in a common supply line to the admission pressure prevailing in the feed lines, always has the drawback of producing large amounts of noise. Since the pressure difference between supply pressure and admission pressure is now lower, the noise is also reduced.
A further advantage of the invention consists in the fact that the system overall becomes harder, i.e. a higher pressure prevails immediately upstream of the narrowest nozzle cross section, with the result that, when liquid phase, e.g. liquid pig iron, penetrates into the nozzle, it is removed again more quickly and thus nozzle damage is reduced.